Current Trends in Cosmology

A special issue of Astronomy (ISSN 2674-0346).

Deadline for manuscript submissions: 15 November 2024 | Viewed by 3407

Special Issue Editor


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Guest Editor
1. SISSA-International School for Advanced Studies, Via Bonomea 265, 34136 Trieste, TS, Italy
2. INFN-Sezione di Trieste, Via Valerio 2, 34127 Trieste, TS, Italy
Interests: cosmology; dark matter; extragalactic astrophysics
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Special Issue Information

Dear Colleagues,

Cosmology currently represents one of the most important frontiers of physics. The mystery of dark matter and the puzzle of dark energy are among the outstanding challenges in this field. On the observational side, there has been an exponential growth in accurate and important data, which will help in establishing the new theories that we need. In this Special Issue, we plan to present current research in this field, including future prospects. All the topics will be discussed from different angles (observational, computer simulations, and theoretical) starting from that concerning the current significant influx of spectacular images of the universe. In detail, the topics of this SI will include:

  • The current cosmological model and its tensions (theory and observations).
  • Dark matter (theory, observations, detection, production).
  • The evolving universe (reionization, first galaxies and their SMBHs, quasars and AGN, the assembly of cosmological structures).
  • Probes of the universe from (new incoming) measurements of the CMB and of its large-scale structure.
  • Multimessenger cosmology (gravitational waves, cosmic gamma and X-rays, neutrinos).
  • Black holes in the universe over 10 orders of magnitude in mass.
  • Astrophysical aspects of cosmology.

Dr. Paolo Salucci
Guest Editor

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Keywords

  • cosmological model
  • dark matter
  • evolving universe
  • CMB
  • multimessenger cosmology
  • astrophysical aspects of cosmology

Published Papers (4 papers)

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Research

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25 pages, 7046 KiB  
Article
A Critical Examination of the Standard Cosmological Model: Toward a Modified Framework for Explaining Cosmic Structure Formation and Evolution
by Robert Nyakundi Nyagisera, Dismas Wamalwa, Bernard Rapando, Celline Awino and Maxwell Mageto
Astronomy 2024, 3(1), 43-67; https://doi.org/10.3390/astronomy3010005 - 12 Mar 2024
Viewed by 981
Abstract
This paper explores the fundamental cosmological principle, with a specific focus on the homogeneity and isotropy assumptions inherent in the Friedmann model that underpins the standard model. We propose a modified redshift model that is based on the spatial distribution of luminous matter, [...] Read more.
This paper explores the fundamental cosmological principle, with a specific focus on the homogeneity and isotropy assumptions inherent in the Friedmann model that underpins the standard model. We propose a modified redshift model that is based on the spatial distribution of luminous matter, examining three key astronomical quantities: light intensity, number density, and the redshift of galaxies. Our analysis suggests that the model can account for cosmic accelerated expansion without the need for dark energy in the equations. Both simulations and analytical solutions reveal a unique pattern in the formation and evolution of cosmic structures, particularly in galaxy formation. This pattern shows a significant burst of activity between redshifts 0 < z < 0.4, which then progresses rapidly until approximately z ≈ 0.9, indicating that the majority of cosmic structures were formed during this period. Subsequently, the process slows down considerably, reaching a nearly constant rate until around z ≈ 1.6, after which a gradual decline begins. We also observe a distinctive redshift transition around z ≈ 0.9 before the onset of dark-matter-induced accelerated expansion. This transition is directly related to the matter density and is dependent on the geometry of the universe. The model’s ability to explain cosmic acceleration without requiring fine tuning of the cosmological constant highlights its novelty, providing a fresh perspective on the dynamic evolution of the universe. Full article
(This article belongs to the Special Issue Current Trends in Cosmology)
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Review

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33 pages, 7491 KiB  
Review
Refracted Gravity Solutions from Small to Large Scales
by Valentina Cesare
Astronomy 2024, 3(2), 68-99; https://doi.org/10.3390/astronomy3020006 - 5 Apr 2024
Viewed by 680
Abstract
If visible matter alone is present in the Universe, general relativity (GR) and its Newtonian weak field limit (WFL) cannot explain several pieces of evidence, from the largest to the smallest scales. The most investigated solution is the cosmological model Λ cold dark [...] Read more.
If visible matter alone is present in the Universe, general relativity (GR) and its Newtonian weak field limit (WFL) cannot explain several pieces of evidence, from the largest to the smallest scales. The most investigated solution is the cosmological model Λ cold dark matter (ΛCDM), where GR is valid and two dark components are introduced, dark energy (DE) and dark matter (DM), to explain the ∼70% and ∼25% of the mass–energy budget of the Universe, respectively. An alternative approach is provided by modified gravity theories, where a departure of the gravity law from ΛCDM is assumed, and no dark components are included. This work presents refracted gravity (RG), a modified theory of gravity formulated in a classical way where the presence of DM is mimicked by a gravitational permittivity ϵ(ρ) monotonically increasing with the local mass density ρ, which causes the field lines to be refracted in small density environments. Specifically, the flatter the system the stronger the refraction effect and thus, the larger the mass discrepancy if interpreted in Newtonian gravity. RG presented several encouraging results in modelling the dynamics of disk and elliptical galaxies and the temperature profiles of the hot X-ray emitting gas in galaxy clusters and a covariant extension of the theory seems to be promising. Full article
(This article belongs to the Special Issue Current Trends in Cosmology)
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Other

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8 pages, 588 KiB  
Brief Report
Constraining the Inner Galactic DM Density Profile with H.E.S.S.
by Jaume Zuriaga-Puig
Astronomy 2024, 3(2), 114-121; https://doi.org/10.3390/astronomy3020008 - 11 Apr 2024
Viewed by 516
Abstract
In this short review, corresponding to a talk given at the conference “Cosmology 2023 in Miramare”, we combine an analysis of five regions observed by H.E.S.S. in the Galactic Center, intending to constrain the Dark Matter (DM) density profile in a WIMP annihilation [...] Read more.
In this short review, corresponding to a talk given at the conference “Cosmology 2023 in Miramare”, we combine an analysis of five regions observed by H.E.S.S. in the Galactic Center, intending to constrain the Dark Matter (DM) density profile in a WIMP annihilation scenario. For the analysis, we include the state-of-the-art Galactic diffuse emission Gamma-optimized model computed with DRAGON and a wide range of DM density profiles from cored to cuspy profiles, including different kinds of DM spikes. Our results are able to constrain generalized NFW profiles with an inner slope γ1.3. When considering DM spikes, the adiabatic spike is completely ruled out. However, smoother spikes given by the interactions with the bulge stars are compatible if γ0.8, with an internal slope of γsp-stars=1.5. Full article
(This article belongs to the Special Issue Current Trends in Cosmology)
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8 pages, 917 KiB  
Brief Report
Possible Tests of Fundamental Physics with GINGER
by Giuseppe Di Somma, Carlo Altucci, Francesco Bajardi, Andrea Basti, Nicolò Beverini, Salvatore Capozziello, Giorgio Carelli, Simone Castellano, Donatella Ciampini, Gaetano De Luca, Angela D. V. Di Virgilio, Francesco Fuso, Francesco Giovinetti, Enrico Maccioni, Paolo Marsili, Antonello Ortolan, Alberto Porzio, Matteo Luca Ruggiero and Raffaele Velotta
Astronomy 2024, 3(1), 21-28; https://doi.org/10.3390/astronomy3010003 - 29 Feb 2024
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Abstract
The GINGER (gyroscopes in general relativity) project foresees the construction of an array of large frame ring laser gyroscopes, rigidly connected to the Earth. Large frame ring laser gyroscopes are high-sensitivity instruments used to measure angular velocity with respect to the local inertial [...] Read more.
The GINGER (gyroscopes in general relativity) project foresees the construction of an array of large frame ring laser gyroscopes, rigidly connected to the Earth. Large frame ring laser gyroscopes are high-sensitivity instruments used to measure angular velocity with respect to the local inertial frame. In particular, they can provide sub-daily variations in the Earth rotation rate, a measurement relevant for geodesy and for fundamental physics at the same time. Sensitivity is the key point in determining the relevance of this instrument for fundamental science. The most recent progress in sensitivity evaluation, obtained on a ring laser prototype, indicates that GINGER should reach the level of 1 part in 1011 of the Earth’s rotation rate. The impact on fundamental physics of this kind of apparatus is reviewed. Full article
(This article belongs to the Special Issue Current Trends in Cosmology)
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